The present invention is directed to a novel paddle wheel wiper for a disk stacker and has particular application in an electrostatographic printing apparatus.
In the process of electrophotographic printing, a photoconductive surface is charged to a substantially uniform potential. The photoconductive surface is image wise exposed to record an electrostatic latent image corresponding to the informational areas of an original document being reproduced. This records an electrostatic latent image on the photoconductive surface corresponding to the informational areas contained within the original document. Thereafter, a developer material is transported into contact with the electrostatic latent image. Toner particles are attracted from the carrier granules of the developer material onto the latent image. The resultant toner powder image is then transferred from the photoconductive surface to a sheet of support material and permanently affixed thereto.
This process is well known and useful for light lens copying from an original and printing application from electronically generated or stored originals, and in ionography.
In the above referenced copending application Ser. No. 07/568,736 a Disk Stacker is described which receives, inverts, stacks and registers sheets against a registration member and has an elongated flexible wiper which moves in timed relation to the rotatable disk engaging sheets near the output position and forcing the sheets to contact the registration member. The wiper is described and illustrated as having an elongated flexible wiping member attached at one end to the shaft about which the disk rotates and a second end having a high coefficient of friction to engage the sheet near the output station. Since the preferred rotatable disk has two diametrically opposed slots, a second wiper is attached to the shaft diametrically opposed to the first one. In practice the illustrated system used wipers with the wiping end made of a conventional polyester polyurethane. While capable of performing adequately this material suffers certain deficiencies, particularly with respect to the variation in the mechanical properties with changes in temperature and relative humidity. The mechanical properties such as resiliency, wear, compression set and tensile set are dynamic properties varying with changes in temperature and relative humidity, thereby, providing unstable paper edge registration alignment. Accordingly, there is a need for an improved paddle wheel wiper having a more stable response in mechanical properties, particularly resiliency, to variations in temperature and relative humidity and in particular, having better wear and compression set characteristics and paper edge registration alignment in electrostatographic apparatus.